Refractory metal alloys for use in oxidation environments

ABSTRACT

A refractory metal alloy comprising principally columbium and titanium with lesser amounts of hafnium, vanadium, tungsten, aluminum, and molybdenum provides excellent resistance to air oxidation at high temperature. The preferred composition range is as follows: Columbium 48-54 percent; Titanium 23-25 percent; Hafnium 9.7517.5 percent; Vanadium 2-8.75 percent; Tungsten 2.25-2.75 percent; Aluminum 1.8 percent; and Molybdenum 0.7 percent; all parts by weight.

EXPOSURE TIME (HOURS) I United States Patent 1 1111 3,753,699 Anderson, Jr. et a1. Aug. 21, 1973 [54] REFRACTORY METAL ALLOYS FOR USE 2,940,845 6/1960 Jatfee et a1. 75/175.5 X [N OXlDATlON ENVIRONMENTS 2,822,268 2/1958 H1x 75/174 [75] Inventors: Anderson Primary Examiner-Charles N. Lovell Huntington Beach; Ralph Attorney-Daniel T Anderson et :al Mendelson, Westminster, both of Calif. [57] ABSTRACT [73] Asslgneez TRW lnc., Redondo Beach, Callf.

A refractory metal alloy compnsmg prmclpally colum- Filed; c- 1971 bium and titanium with lesser'amounts of hafnium, va- [21] AppL 214 351 nadium, tungsten, aluminum, and molybdenum provides excellent resistance to air oxidation at high tem- [52] U 8 Cl perature.

75 174 [51] Int. Cl. C221: 27/00 The preferred composltlon f as follows' [58] Field of Search 75/134, 174, 175.5 Columbwm 48-54 Percent; Tltanwm 23-25 Percent; Hafnium 9.75-l7.5 percent; Vanadium 2-8.75 [56] References Cited 1 percent; Tungsten 2.252.75 percent; Aluminum 1.8 UNITED STATES PATENTS percent; and Molybdenum 0.7 percent; all parts by ei ht. 3,028,236 4/1962 Wlodek et a1. 75/174 w g 3,317,314 5/1967 Wlodek et a1. 75/174 2 Claims, 2 Drawing Figures I O O 4 501- /o "5OG1- 0/6 2! 501 /0 Ti |200 C 8 O PRIOR ARI/ g ALLOY PRESENT ALLOY 1300 C E U fi o 4 O C SHEET 1 0F 2 PATENTEU M1821 I973 .DC A

R VI BTW RRL PA O O O O 8 6 4 2 EXPOSURE TIME (HOURS) BACKGROUND OF THE INVENTION This invention relates to new and improved refractory metal alloys. More specifically, this invention relates to refractory metal alloys having columbium and titanium as the principal alloy ingredients; hafnium, vanadium, tungsten, aluminum, and molybdenum are minor constituents.

Refractory alloys have been employed as castings, forgings, etc., at high temperatures.

Typical examples of refractory alloys are found in US. Pat. Nos. 3,086,859; 2,940,845; 2,991,197; 2,880,088; 2,819,960; 2,754,204; and 3,368,881.

However, their use at high temperature in an oxidizing environment is limited since the amount of oxidation continues with increasing time. Eventually, this results in failure of the alloy as it becomes converted into an oxide.

It is, therefore, an object of the present invention to provide a refractory alloy which may be employed as castings, forgings, etc., in a high temperature, oxidizing environment such as air.

Other objects will be disclosed from the description and graph to follow.

According to the invention, the broad range of the components in the refractory alloy is as follows:

Columbium 48-54 percent; Titanium 23-25 percent; Vanadium 2-8.75 percent; Hafnium 9.75-17.5 percent; Tungsten 2.25-2.75 percent; Aluminum 1.8 percent; and Molybdenum 0.7 percent; all parts by weight percent.

A narrower range of components is as follows:

the relationship between exposure times and weight gain (due to oxidation) of the alloy compositions at various oxidation temperatures in air.

FIG. 1 shows a comparison of the oxidation resistance in air of composition'4 with that of a typical prior art refractory'metal alloy having the composition 45 at. Nb; 50 at. Zr; 5 at. Ti. lt is noted that the curve of composition 4 at l,300 C is well below that of the prior art alloy when exposed to air at 1,200 C; this represents a significant improvement in oxidation resistance.

In FIG. 2, it will be observed that composition 2 performs about as well at 1,300 C as the prior art alloy does at 1,200 C. Also, at l,300 (C, composition 3' performs significantly better than does the prior art alloy at 1,200" C.

It will also be observed in P16. 2 that small changes in the alloy composition can be critical to oxidation resistance. For example, decreasingfthe concentration of columbium (from 49.5 to 46.5 percent) while increasing the vanadium content (from 5 .3 to 8.3 percent) results in an alloy having poor oxidation resistance.

The melting point of the present alloy was found to be in excess of 1,700' C; this is at least comparable to refractory metal alloys of the prior art.

Hence, the alloy compositions of this invention are markedly superior to prior art alloys in terms of resistance to air oxidation at high temperature. This factor along with their high melting point renders them well suited for use at high temperatures in air as forgings,

castings, etc.

We claim: l. A refractory alloy consisting of:

Columbium 49.5-52.5 percent; Titanium 23-25 per- Columbium 48-54 percent; Titanium 23-25 percent; cent; Hafnium l0-l6.5 percent; Vanadium 2.25-8.5 Hafnium 9.7S-17.5 percent; Vanadium 28.75 percent; Tungsten 2.5 percent; Aluminum 1.8 percent; percent; Tungsten 2.25-2.75 percent; Aluminum and Molybedenum 0.7 percent; all parts by weight per- 1.8 percent; and Molybdenum 0.7 percent; all parts cent. by weight.

Specific alloy compositions of this invention are: 2. A refractory alloy consisting of:

Composltlon Columbium Titanium Hatnlum Vanadium Tungsten Aluminum Molybdenum 1 52.5 24.0 10.2 s. 2.5 1.8 0.7 2 52.5 24.0 13.2 5.3 2.5 1.8 0,7 t 3 52. 5 24. 0 16. 2 2. a 2. 5 1. s o. 7 4 49. 5 24. 0 16.2 5. 3 2. 5 1. s 0.1

Columbium 49.5-52.5 percent; Titanium 23-25 percent; Hafnium 10-165 percent; Vanadium 2.25-8.5 percent; Tungsten 2.5 percent; Aluminum 1.8 percent and Molybdenum 0.7 percent; all

parts by weight. 

2. A refractory alloy consisting of: Columbium 49.5-52.5 percent; Titanium 23-25 percent; Hafnium 10-16.5 percent; Vanadium 2.25-8.5 percent; Tungsten 2.5 percent; Aluminum 1.8 percent and Molybdenum 0.7 percent; all parts by weight. 